The reason for that is that the Pre, the Droid, and the iPhone all use a similar graphics chip of the Power VR variety. Snapdragon phones use the AMD Z340 I believe. Gameloft first started writing all those fancy 3d games for the iPhone, and then they were ported to the Palm Pre, and later to the Droid. Because of this, the code doesn't seem to be optimized for Snapdragon equipped phones. Gameloft takes a bit of a lazy route (understandably) and is just doing direct ports. Also, another thing to consider is that the Pre and the iPhone both use 320 x 480 resolution. I have not seen Asphalt 5 (most popular game for all 3 platforms from Gameloft) actually run on a Droid, so I am not sure if the game runs in native resolution (which is oddball to begin with 480 x 854 instead of 480 x 800) or if it runs at 320 x 480.
Either way, I have high hopes that the popularity of the Snapdragon platform will make 3d game designers optimize the games for it.
I have yet to find a technical review of just the 3d chips in both platforms to see which really is faster or more suited to games.